The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
The generally acknowledged most significant operational difference between a conventional vehicle powertrain and one configured for engine start-stop operation is the delay the driver experiences before feeling acceleration during an autostart event. Whereas the engine of a conventional vehicle remains running at idle when the vehicle is, for example, stopped in traffic, so that when the brake is released and the accelerator pedal is depressed, engine speed quickly increases above idle and the degree of torque converter coupling and torque delivery through the transmission rapidly increases, in an engine start-stop powertrain, after the brake is released and the accelerator is depressed, the engine must first crank and re-start and then, as engine speed increases, begin to transmit torque through the torque converter and the transmission.
Although it would appear that the sequence of engine start and speed ramp up are primarily responsible for the vehicle motion and acceleration delay, it has been found that some delay is caused by the fact that torque throughput cannot be quickly established through the fluid coupling of the torque converter, especially when the input to the torque converter and thus the torque converter pump were previously stationary due to the stopped engine.